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  • Voltage Regulated [5v] Bicycle Dynamo Light & USB Charger

    "there are NO resistors in my circuit."except that, you see... that LM7805 chip is, essentially, a big 'ol self-adjusting resistor. When the output drops below 5V it adjusts its resistance down, when output goes above 5V, it increases its resistance, which is how it functions as a regulator. A 7805 is dead simple to wire up, but they aren't used where efficiency matters... if you hook one up to a 10V supply you are gonna automatically be wasting 50% of your energy as heat (which is why it comes in the package with the big heat sink tab.)Good next step would be to search for "buck converter" which is a more efficient form of voltage regulation.

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